This invention relates to radiation emitting systems.
Known radiation emitting systems include a radiation emitter, such as a light emitting diode (LED), an electrical power source for driving the emitter and, in most practical applications, a switching transistor for applying power to the emitter in pulse form under control of appropriate oscillator or switching amplifier circuitry. Typical systems of this type utilize a direct current power source, or a direct current source in combination with a charging capacitor, to drive the emitter with square wave or generally similar pulses of such width and frequency that the emitter is pulsed off and on for substantially equal intervals of time. Refer, for example, to U.S. Pat. Nos. 3,894,229, 3,928,760, 3,657,543, 3,751,671, 3,742,947, 3,909,670, 3,705,986 and 3,486,029. Another generally similar direct current system, disclosed in U.S. Pat. No. 3,727,185, utilizes a silicon controlled rectifier (SCR) to switch the emitter. Still another system, disclosed in U.S. Pat. No. 3,924,120, converts alternating current electrical power to 120 Hz square wave, the pulse width of which is controllable for information transmission to remote locations.
These and other radiation emitting systems are of limited power and, hence, tend to be short ranged, especially in dust filled or like environments. Although most commercially available semiconductor radiation emitters are capable of peak power operation for short time intervals, in most practical application ---- both continuous or pulse operated -- they are operated at average power levels well below peak power because of fears of excessive junction temperatures, and other factors. Thus, the effectiviness of most radiation systems heretofore has been limited by unacceptably low emitter power levels, or emitter current limiting devices, or both. The effectiveness of systems which utilize capacitive emitter charging elements are further limited by dielectric heating effects and capacitor charging time limitations.